In a stringed musical instrument, such as a guitar, the strings, placed under tension, extend unsupported between a first critical point usually formed by the nut positioned where the neck joins the head and a second critical point usually formed by a clearly defined point on the bridge positioned on the body. The strings are secured or fixed at one end on the body of the instrument to what is traditionally known as the tailpiece, strung over the bridge and extended past the nut at the transition from the neck instrument to the head, and, for conventional instruments, secured at the other end to the tuning pegs where an untensioned string is tensioned and adjusted to a tuned pitched condition, proper playing pitch for play, or, simply, tuned condition; sometimes a nut arrangement is provided for a headless or tuning peg-less design. The neck further comprises a fingerboard or fret board that a player presses the strings against to play various pitches up and down the neck; the fingerboard typically is formed with a convex radius that commonly varies between 9 and 16 inches. Further, it is known to those of ordinary skill in the art that the direction of the strings are generally parallel to both neck and the surface of the body despite instances where the string deviates from this direction at either or both the peg head or tailpiece. The tension of an individual guitar string is approximately 17 lbs at typical pitched conditions; anchoring or securely attaching the string holds the string to the instrument under normal conditions that often comprise an additional of 10 lbs of tension per string under other certain circumstances.
The second critical point can be created as a part of a combined bridge and tailpiece structure. Traditionally, the size of the bridge element is quite small so as to create a clearly defined single point of contact between the string and the bridge element. It is between these two points that the playable string length is typically determined, sometimes referred to as the scale length or harmonic length. Adjusting the relative distance between the first and second critical points is called harmonic tuning or setting the intonation. Some bridges structures are individually adjustable, that is for each string, relative to the nut for achieving a more precise harmonic tuning. Usually this adjustment of the second critical point for harmonic tuning is carried out first and then the strings of the instrument are tuned to playing pitch. Often referred to the “initial setup”, it is not uncommon that further adjustment of the harmonic tuning is necessary for a variety of reasons, for example, including changing the brand of a string where the alloy of the strings is varied or when the gauge of strings the player chooses changes as well as “setting” the string by manually pulling on the string along the scale length in order to improve elasticity in the string at first tensioning before the string can confidently relied on to hold proper playing pitch during the life of the string.
Often the typical construction of the strings, particularly for guitar and bass, includes a plain end and, on the other end, a “ball end” which being a washer-like addition is wrapped by the string itself into a larger form to enable “fixing” or securing the string on the instrument to the tailpiece element; alternatives to the “ball end” include as known to those of ordinary skill in the art as “bullet ends” formed from metal and molded around the end of the string. The tailpiece is usually provides for an opening or recess sufficient in size to receive the strings of various diameters ranging from 0.007″ to 0.070″ or more while being smaller than the diameter of the ball end so as to limit the passing of the ball end through the opening or recess in order to secure or mount each of the individual strings to the body. The wrapping usually extends up to a ½″ towards the plain end and as such the position of the tailpiece structure relative to the bridge element must insure that the wrapping does not extend over the second critical point when arranged on the instrument; this wrapping, under normal circumstances, is not subject to stretch compared to the rest of the string. Stable fine adjustments of these and other elements have been a longstanding problem for stringed musical instruments.
In the relevant art, “anchoring” strings is often referred to as attaching or securing a string and understood with the limitation that the anchoring is sufficient so that the string is fixedly attached or secured to the instrument under the typical tensioned conditions of the string that typically range from 16 to 20 lbs or greater.
Playing pitch or proper playing pitch or pitched string condition is generally understood by one of ordinary skill in the art to be the proper pitch of a guitar string relative to the remaining guitar strings when a guitar is played “in tune.” For example, in a standard tuning arrangement, for a six string guitar, based on the standard A=440 Hz, the playing pitch of the 1st string (highest) is tuned to note E (329.63 Hz), the playing pitch of the 2nd string is tuned to note B (294.94 Hz), the playing pitch of the 3rd string is tuned to note G (196.00 Hz), the playing pitch of the 4th string is tuned to note d (146.83 Hz), the playing pitch of the 5th string is tuned to note A (110 Hz), and the playing pitch of the 6th string is tuned to note E (82.41 Hz).
In the Proelsdorfer U.S. Pat. No. 2,304,597, string tensioning devices placed on the tailpiece for fine tuning the pitch of the strings of violins, guitars and the like, were disclosed; such pitch adjustment is quite limited in range, comprising generally an interval falling between that of a whole tone and a major third at best, and designed to offer the tuning of the strings a minor adjustment of pitch after the general tuning is achieved with the tuning pegs on the head of the instrument which traditionally first provides for raising and adjusting the tension of the strings to pitch from an untensioned condition and then setting the string. This is regarded as fine tuning and the apparatus for doing so, the “fine tuners”, usually comprise an adjustment knob or thumb screw.
It is known to those skilled in stringed musical instrument design and construction that various tremolos have been proposed and utilized for varying the tension of all the strings simultaneously for the purpose of creating a tremolo sound. Further, it is known to those skilled in the art that there are a great many commonly used names for such devices, such as tremolo, tremolo device, tremolo tailpiece, tremolo bridge, fulcrum tremolo, fulcrum tremolo bridge, fulcrum tremolo tailpiece, fulcrum tremolo bridge-tailpiece, vibrato, vibrato bridge, vibrato tailpiece, vibrato bridge tailpiece, etc.
In one specific species, known as the fulcrum tremolo, first introduced in Fender U.S. Pat. No. 2,741,146, shows and provides a device comprising a novel structure, which incorporates the bridge and the tailpiece. The portion supporting the bridge elements is called the bridge plate or the base plate. Further, both the bridge and the tailpiece elements connected to the base plate both move together as the fulcrum tremolo device is pivoted. Accordingly, a singular and defining aspect of the fulcrum tremolo is that the harmonic tuning is upset as the device is pivoted; and, accordingly, for an instrument equipped with a fulcrum tremolo, it is unique in that only restoring all of the strings to a proper pitched condition also simultaneously restores the harmonic tuning for all the strings. The base plate upon which the individual bridge elements are adjustably secured has a beveled ridge portion which is secured to the instrument body by six screws permitting pivotal movement about a fulcrum axis which varies the tension on the strings and produces the desired tremolo effect; in general, this device allowed for extensive dropping down of the pitch of all the strings and a modest upward capacity that further enabled the familiar mild pedal steel or Hawaiian guitar vibrato effect provided in gentle pivoting.
In this first vintage fulcrum tremolo, herein referred to as Type I, the metal bridge elements of '146 are loosely held in place by a spring loaded attachment screw arrangement pivotally secured through openings in a small folded portion of the base plate farthest from the fulcrum axis. The bridge elements also incorporate set screws for varying the relative height of the bridge elements and, therefore, height of the respective second critical points relative to the base plate and by extension, to the body and neck. Later iterations of Fender '146 included pivotally supporting the fulcrum tremolo relative to the body with a riser post arrangement adjustably connected to the fulcrum tremolo. The horizontal distance between the vertical centerline of each riser post is approximately 2.22″. Further, the distance from the pivot point to the second critical point not including the variable heights of the bridge elements is 0.25″ and the distance form the nut to the pivot is about 25.25″ since the Fender Stratocaster for which this fulcrum tremolo first appeared provided a 25.5″ scale length.
Typically, in order to facilitate the fulcrum tremolo pivoting about its fulcrum axis, counter springs, as a biasing element, are utilized to counteract or counter balance the pull of the strings. Counter springs are usually connected to the body of the instrument at one end and, on the other end, to a separate spring attachment means transverse the base plate, usually a block of metal, milled or cast or a combination of the two, which being secured to the bottom of the base plate by three screws 90 degrees to the base plate, is often called a spring block or inertia block. Upward pitch changes initiated by the use of the fulcrum tremolo in one direction can significantly increase the tension of individual strings.
One of the most troublesome problems with prior art for the fulcrum tremolo has been maintaining the “initial position” achieved at “initial setup” when all the strings are brought to proper playing pitch as the harmonic tuning is achieved. When a musician plays on the string there is usually some kind of string stretch over time that results in the overall tuning, and thereby, the “initial position” going out of balance. Specifically, when the pitch of the string changes, the position of the fulcrum tremolo and the position of the second critical point relative to the nut changes which then instantly alters the harmonic tuning.
This singular characteristic adds complexities in obtaining the primary goal of achieving a stable equilibrium between the force of the tension provided by the two to five biasing or counter springs (connected between the tremolo and the body) in relation to force of tension of all the strings (connected to the fulcrum tremolo and the end of the neck at the peg head by the tuning pegs or an optional nut arrangement that secures the strings without tuning pegs, etc.)
Accordingly, these and other inherences need to be addressed in achieving a true and lasting initial position for the fulcrum tremolo and has been the object of many inventions. In this inherent inter-dependant system of tensioning forces, contrary to the requirements of other tremolo or fixed bridge arrangements, (in the ideal instance where the essential conditions of the initial setup have been established and the appropriate tensioning force of the springs provisioned), the precise tensioning to proper playing pitch for any less than the total number of strings will inherently fail to achieve pitch and harmonic tuning for all of those strings attached to the tremolo.
Initial position refers to the position of the fulcrum tremolo and, therefore, the position of the second critical point on the bridge elements in relation to the first critical point on the nut such that the tension of the strings, each at the intended proper pitched condition, and the appropriately tensioned counter springs, renders a specific equilibrium point wherein the harmonic tuning for all the strings is simultaneously achieved. Often the pivot means is subject to wear and the tremolo does not always return to its initial position. Great care is required to establish the initial position since both aspects of adjustment are interactive and it simultaneously provides both the proper harmonic tuning and proper pitch tuning for each of the individual strings in order to enable a lasting “initial setup”.
Improvements to the Fender '146 fulcrum tremolo have included using string clamps at the nut and at a point on the opposite side of the intonation point or second critical point on each of the bridge elements relative to the nut in order to limit string stretch to the prime vibratory portion of the string within these two points defining the scale length; and, separately, adopting a novel shaped beveled edge, called a “knife edge”, adjustably supported by two screw-like members called riser posts positioned in the body to improve the return to initial position after pivoting the fulcrum tremolo device (Rose U.S. Pat. No. 4,171,661). The knife edge fulcrum pivot arrangement provides for the base plate to be positioned generally parallel to the instrument body and offers the novel possibility to increase the tension of the string for upward pitch changes.
In this second vintage fulcrum tremolo, herein referred to as Type II, the horizontal distance between the vertical centerline of each riser post is approximately 2.925″. The distance from the pivot point to the second critical point, not compensating for the variable heights of the bridge elements, is about 0.425″ and, approximately, 25.00″ from the first critical point on the nut for instruments with a 25.5″ scale length.
In Rose U.S. Pat. No. 4,497,236 a combination of the bridge element, the tailpiece and fine tuners replaced the “novel structure” of the Fender device so that within the limited range (typically within a range about the interval of a whole tone, for example from C to D in the Western diatonic musical scale) the strings could be re-tuned without first unlocking the string clamps at the nut. However, string stretch beyond the range of the fine tuners necessitated a correction that is tedious and time consuming involving unlocking the string clamps, re-tuning the strings, re-clamping, and further re-tuning the string with the fine tuners and then re-tuning all the other strings to re-balance the equilibrium point back to initial position. The string clamps of the Rose fulcrum tremolo are characterized by small blocks slideably mounted within a recess within a housing element connected to the bridge element. The player typically cuts the ball-end of the string off and then vertically places the cut end of the string within the recess between the block and a vertical surface located closest to the bridge element created by the recess and then bend in the direction of the tuning pegs—in a some instances, there are later designs that do not require the ball end to be cut off for the clamping mechanism to fixedly secure a string.
Therefore, for stringed musical instruments, as is known to those skilled in the art:                The second critical point is a clearly defined point on the bridge or individual bridge elements, the adjustment of which relative to the first critical point on the nut defines the length of the string or scale length and the adjustment of which is called harmonic tuning.        
For fulcrum tremolos as originated by Fender U.S. Pat. No. 2,741,146, when pivoted:                Both the bridge portions and the string anchoring means, the tailpiece, simultaneously move about a common fulcrum axis;        The harmonic tuning is upset and is only restored when all strings are at proper playing pitch;        The tuning pegs or other means of tensioning the strings are inter-dependant with each other in obtaining initial position; and        Various factors can disturb the equilibrium point between the tension of the strings and the tension of the counter springs and as a consequence disturb the initial position.        
For those fulcrum tremolos equipped with fine tuners as with Rose U.S. Pat. No. 4,497,236, Storey U.S. Pat. No. 4,472,750 and Fender U.S. Pat. No. 4,724,737:                The bridge and tailpiece portions simultaneously move about the fulcrum axis when the device is pivoted for the tremolo effect;        The fine tuner screws simultaneously move with the bridge and tailpiece portions about the tuning axis when fine tuning; and        Fine tuners are designed to offer the tuning of the strings a minor adjustment of pitch after the general tuning is first achieved, typically, by the tuning pegs on the head of the instrument; and        Adjusting the tension of a string by the fine tuner knob alone simultaneously adjusts the harmonic and pitch tuning and can achieve tuning a string to proper pitch conditions while simultaneously achieving proper harmonic tuning.        
For those fulcrum tremolos fitted with string clamps at the first and second critical points as in Rose U.S. Pat. No. 4,171,661,                String stretch beyond the clamps at the first and second critical points is eliminated offering the most stability of tuning possible; and        A plain end of the string is inserted between the bock and a vertical surface formed, transverse the general direction of the string, in a recess in the housing element and clamped by threading an adjustment bolt; the adjustment screw is pivotally positioned in the direction of the strings and the fine tuner adjustment screw is both transverse to the adjustment bolt and direction of the strings.        
These two vintage fulcrum tremolos of the last century, Fender in the 50's and Rose in the 80's, are in part distinguished by the differing standards in the spacing between the riser posts, approximately, 2.22″ and 2.925″ typically. The individual parts of the two vintage designs were generally not compatible. Consequently, those who had guitars with the 2.925″ spacing were limited to tremolos that had fine tuner arrangements and string locks and those guitars with the 2.22″ spacing were limited to those tremolos without fine-tuners and string locks.
Often the musician is called upon to play in an ensemble where the other instruments are not tuned to a typical concert pitch. Accordingly, the musician must flatten or sharpen the initial tuning of all the strings on his instrument in order to meet the pitch requirements of other instruments. This re-tuning often disturbs the initial position because the tension of the counter springs has not been readjusted as well. Accordingly, the position of the base plate of the tremolo is either tilting away from or towards the body of the instrument which then can limit the range in which the tremolo can be activated. Steinberger U.S. Pat. No. 4,632,005 and Gunn U.S. Pat. No. 4,955,275 provide for an adjustable counter spring and utilize an adjustment knob that provides a means to vary tension of the counter spring and thereby maintain the equilibrium point between the tension of the counter spring and the tension of the strings on a non-fulcrum tailpiece tremolo, that is, a tremolo device where the bridge elements do not pivot with the anchoring means and, therefore, do not upset the harmonic tuning as such.